I managed to do it with official customer support. They were helpful even though I admitted the DVR was abandoned in an business place and I had no previous records on it.
Is this possible with DS-7208HQI-K20820180821CCWRC44711516WCVU?
V3.5.37 build 180801
I'm not really experienced with this stuff, I must be doing something wrong or entering something incorrectly. I checked the start date.